Spark arrester



March 5, 1968 .LKRIZMAMr JR SPARK ARRESTER Filed De. 8, 1965L UnitedStates Patent Oiitice 3,371,472 SPARK ARRESTER .lohn Krizman, Jr., 10549Monogram Ave., Granada Hills, Calif. 91344 Filed Dec. 8, 1965, Ser. No.512,457 3 Claims. (Cl. 55-399) ABSTRACT F THE DlSCLSURE A spark arresterfor internal combustion engines, having axially aligned inletand outlettubes, the inlet tube having a closed end extending into a casing, and aspiral spark arrester around the inlet tube in the casing arranged toreceive a portion of incoming gases, and means for passing anotherportion more desirably to the outlet tube to preclude buildup ofexcessive back pressure.

This invention relates to a spark arrester for internal combustionengines. More particularly, this invention relates to a spark arresterfor small internal combustion piston engines, such as those inmotorcycles and generators, particularly suitable for use in proximityto brush, timber and similar cellulosic materials.

Spark arresters for small displacement internal combusion engines invehicles such as motorcycles or other trail vehicles, or in generators,used in proximity to forests, must conform to standards which establishminimum performance and maintenance requirements designed to minimizethe risk from exhaust spark fires.

The performance of spark arresters is measured by arresting efficiency,which is dened as the percent of carbon particles retained or destroyedby the spark arrester when tested under prescribed conditions in astandard apparatus. An arresting efficiency of at least 80 percent isrequired for all ow rates from l percent of the rated minimum How rateto the rated maximum ow rate. The rated maximum ow rate is defined asthe maximum rate of flow at which the back pressure i.e., thedifferential pressure from intake to discharge of the arrester, is onepound per square inch. The rated minimum flow rate is dened as ten timesthe lowest ow rate at which 8Ol percent arresting efficiency isobtained. The rated ow range of the arrester is the range of ow rates,in cubic feet per minute, between the rated maximum flow rate and therated minimum flow rate. Upon determination of the rated ow range of aspecic spark arrester, it may be applied in the system of an enginewhich has an exhaust flow rate within the rated flow range underoperating conditions of maximum speed and power.

In prior art spark arresters for small displacement engines thereresults a substantial drop in arresting elticiency when the backpressure exceeds about one pound per square inch. The present inventioneliminates this critical back pressure problem and provides a sparkarrester having a high arresting efficiency at one pound per square inchback pressure, and in which there is no substantial drop in efficiencywith an increase in back pressure beyond this limit,

The present invention further provides a spark arrester adapted torequire less metal for construction, as well as fewer welding andbrazing operations, than prior art devices, resulting in substantialimprovements in the construction and assembly of such devices. The sparkarrester of the present invention is adapted also to be combined withstandard muffler systems in small displacement engines, for example upto about 15 cubic inches, and to operate in a vertical, horizontal orinverted position at very high arresting eliiciencies without anincrease in the velocity of the exhaust gases.

3,371,472A Patented Mar. 5, 1968 The spark arrester of the presentinvention is comprised of an inlet tube having a closed end, and anoutlet tube, the closed end of the inlet tube and an end of the outlettube extending into a spiral arresting means contained within a largertubular outer shell or casing which forms a carbon trap. The open end ofthe inlet tube is in communication with the engine exhaust and theoutwardly extending end of the outlet tube is in communication with theatmosphere. The inlet tube is provided with a longitudinally extendingoutwardly directed opening for discharge of exhaust gas and carbonparticles into the arresting means. The arresting member is providedwith opening means for discharge of the carbon particles into the carbontrap formed by the walls of the arresting member and the shell. rl`heinlet tube and outwardly directed opening thereof are positioned in suchrelationship to the arresting member and its opening that a passage iscreated between the outwardly directed opening in the inlet tube and thecarbon trap whereby a travel path is provided from the inlet tube to thecarbon trap for the carbon particles and from the inlet tube to theoutlet tube for the exhaust gas. When the particles and gas impinge uponthe closed end of the inlet tube, they are forced to be discharged fromthe tube into the arresting member in a spiral motion through theopening. The relatively heavy carbon particles are thrown outwardly andcontinue to travel along the inner wall of the arresting member in aspiral travel path and are discharged through the opening of thearresting member to the carbon trap from which they may be removed. Therelatively light exhaust gas continues to travel with a spiral motion inthe arresting member until it is discharged to the atmosphere throughthe outlet tube, or impinges upon an end wall of the arresting memberwhereby a circular motion is imparted to the gas, causing those carbonparticles which remained in the gas stream to whirl with the gas in thearresting member and be discharged through the arresting members openinginto the carbon trap. Spark arresters having the above structure haveconsistently surpassed the established performance and maintenancerequirements and have been proven to possess extremely high arrestingeiiiciencies and to substantially maintain the same beyond the previousone pound per square inch back pressure limit. For example, arrestingeiciencies in exces sof 96 percent were obtained at 24 c.f.m. and onepound back pressure and in excess of 94 percent at 42 c.f.m. and fourpounds back pressure.

It is an object of this invention, therefore, to disclose and provide aspark arrester for small displacement internal combustion engines havinga high arresting eliiciency.

It is another object of this invention to disclose and provide a sparkarrester for small displacement engines in motorcycles, other trailvehicles, and generators which are used in proximity to cellulosicmaterials.

It is another object of this invention to disclose and provide a sparkarrester including passage means from an inlet tube to an outlet tubefor exhaust gas from an engine, and from the inlet tube to a carbon trapfor carbon particles contained in the exhaust gas.

It is another object of this invention to disclose and provide a sparkarrester for internal combustion engines having a high arrestingeiciency which is substantially maintained as the back pressure duringoperation increases above one pound per square inch.

It is another object of this invention to disclose and provide a sparkarresting device for internal combustion engines, including a singlecontinuous spiral chamber formed by the union of an inlet tube andarresting member.

It is another object of this invention to disclose and provide a sparkarrester for internal combustion engines-- tube at edge portion 23. Asshown having a displacement up to about cubic inches and FIG. l is aperspective view, partly in section, showingy the spark arrester of thepresent invention;

FIG. 2 is a longitudinal sectional View taken along lines Il-II in FIG.l, showing the inlet and outlet tubes extending into the tubulararresting member contained in the tubular carbon trap, and thelongitudinal openings in the inlet tube and arresting member;

FIG. 3 is a transverse section along line III--III of FIG. 2 showing theopening in the arresting member permitting discharge to the lcarbontrap;

FIG. 4 is a transverse section along line lV-IV of FIG. 2 showing thecontinuous spiral chamber formed by the longitudinally abutting inlettube and arresting member, and the openings permitting discharge ofcarbon particles and exhaust gas.

Referring to FIGS. l and 2, the spark arrester 10 of the presentinvention comprises an inlet conduit 11, which may be a tube, having aclosed end 12 and an outlet conduit 13, which may tbe a tube; the,outlet tube is shown mounted in wall 16. Inlet tube 11 is shownextending through wall 17 of the outer shell or casing 30, the closedend 12 of such inlet tube terminating in proximity to the outlet tube13, with which it is in axial alignment. The inner wall of the shell andouter wall of the spirally formed arresting member 14 dene a car-bontrap 15 into which the carbon particles of the exhaust gas discharge.End plate 16 closes oil one end of arresting member 14 and carbon trap15, and end plate 17 closes off the opposite ends of the arrestingmember and carbon trap. End plate 16 may be provided with an .opening 18through which outlet tube 13 extends in sealed relationship with the endplate. End plate 17 may be provided with an opening 19 through whichinlet tube 11 extends in sealed relationship with the end plate. Theclosed end 12 of inlet tube 11 may be disposed in longitudinally spacedrelationship with the open, inward end 20 of outlet tube 13 which is,perferably axially aligned with inlet tube 11. The opposite end ofoutlet tube 13 communicates with the atmosphere.

The open end of inlet tube 11 extends outwardly and may communicate withan engine exhaust pipe. It may be secured thereto by bolts or othersuitable securing means. The inlet tube may -be adapted to be combinedwith standard muffler systems utilized in small displacement internalcombustion engines.

A best seen in FIGS. 2 and 4, inlet tube 11 may be provided with adischarge opening which may be an opening extending longitudinallysubstantially along the inwardly extending portion of the tube,preferably in the form of a longitudinal slot 21. One method of formingthe outwardly directed opening from the tube is to form a slitlongitudinally in the wall of the tube. Longitudinal edge portion 23 ofslot 21 of the inlet tube may preferably be ared outwardly way fromlongitudinal edge portion 31 as shown in FIG. 4, to increase thecircumference of the in the drawings the outwardly directed openingformed in inlet tube 11 preferably extends from the end wall 1'7 towardsthe closed end 12 of the tube but terminates at a point spaced from suchclosed end. This longitudinal edge portion 23 of the tube may besecured, by means of welding or by other satisfactory means, tolongitudinal edge portion 24 of a spirally formed arresting member 14whose exterior iongitudinal and unsecured edge is indicated in FIGS. land 2 at 25. Longitudinal edge portion 26 of member 14 which definesopening 22 may be similarly flared outwardly. Consequently `a singlespiral chamber 27 may be formed by the union of the inlet tube and thearresting member and a continuous spiral travel path provided formovement of the carbon particles from the inlet tube until they areeventually discharged into carbon trap 15. It `will be noted that thelongitudinal marginal edge portion 26 of the spirally formed arrestingmember 14 is virtually above the marginal edge 24 (see FIG. 3); thesetwo edges 26 and 24 extend in a Zone encompassed by a narrow radialangle; the spacing between these edges forms an opening 22 discharginginto trap 15. Edge portion 26 of member 14 approaches but does notcontact the inner surface of casing 30.

As best seen in FIGS. l and 2, and as shown by the arrows indicatingdirection of flow, the stream of exhaust gases and the incendiary carbonparticles 28 contained therein, enter inlet tube 11 and travel inlongitudinal ilow along the tube until they impinge upon the wall ofclosed end 12 of the inlet tube, whereby they are forcibly laterallydischarged through the opening 21 into arrest ing means 14 with a changein direction of ilow (see arrow A) from longitudinal flow to spiralilow. Compared to the weight of the gaseous particles, the relativelyheavy carbon particles, due to centrifugal force, tend to hug the innerwall of the arresting member, travelling :along the continuous spiraltravel path in spiral chamber 27 formed by the union of the cham-bers ofinlet tube 11 and arresting member 14, (see arrow B) until they aredischarged through opening 22 into carbon trap 15.

The stream of exhaust gas continues to travel in spiral llow in thearresting means (see arrow D2) until it is discharged through opening 20in outlet tube 13 to the atmosphere. A portion of the gas streamremaining in the arresting member impinges upon the inner surfaces ofend plates 16 and 17, thereby imparting a circular motion to the gas andcausing the remaining carbon particles in the gas stream to whirl withthe gas stream until discharged through opening 22 into carbon trap 15(see arrows `B and C) and then around edge portion 25 to opening 20 (seearrows D and E).

To facilitate the removal of carbon particles from the carbon trap,outer shell 30 may be provided with an opening means 28a, preferably inthe form of an elongated slot, as shown in FIG. 2. During normal engineoperation, the slot is covered by a closure means 29 which may be a bandsecured circumferentially around the shell, by a bolt or similar meansto eifect an air-tight seal. When it is desired to remove the carbonparticles from the car-bon trap, band 29 is removed from the shell andthe engine is operated, whereby the exhaust pressure causes theparticles to be discharged through opening 28a into the atmosphere. Tooperate in an inverted position, the carbon trap may be extended towardsthe outwardly extending end of the outlet tube and a clean-out openingprovided in the shell adjacent that end.

The longitudinal openings or other discharge means in the inlet tube andarresting means may be adjusted to determine the velocity of the gas.The total iiow area in the opening provided in the inlet tube maypreferably be adjusted to be substantially equal to the total flow areaof the inlet tube so as to effect no increase in velocity, although acharge in Idirection of ilow is effected in the arrester. The opening inthe arresting member may be similarly adjusted.

To assemble the spark arrester of the present invention, the inlet tubeand arresting member may first be sealed together, for example, bywelding or otherwise joining a longitudinal edge of the longitudinalslot of the inlet tube to a longitudinal edge of the slot of thearresting member. The single chamber thus formed may be inserted in theshell along with the outlet tube, and the end plates aflixed thereto toposition th@ member and outlet tube as herein indicated.

The present invention thus provides a compact spark arresting devicewhich requires a minimum amount of metal, is assembled `quickly andoperates efficiently over a large range of back pressure conditions.

It is to be understood that various modifications may be made by thoseskilled in the art without departing from the spirit and scope of thepresent invention as dened by the appended claims.

I claim:

1. A compact spark arrester for an internal combustion enginecomprising:

a cylindrical casing having opposed end walls;

a discharge tube extending through an end wall of the casing;

an inlet tube extending axially through the opposing end wall into saidcasing, said inlet tube having a closed end in proximity to thedischargetube; said inlet tube being longitudinally slit for a portion of itslength within the casing from adjacent said opposite end wall to a zonelongitudinally spaced from the closed end of the inlet tube, onemarginal edge portion of the tube at said slit :being outwardly flaredto form an outwardly directed opening;

an arresting member of spiral form positioned longitudinally in saidcasing and surrounding said inlet tube, a portion of the innerlongitudinal marginal edge of such member being sec-ured to the ii'arededge portion of said tube;

whereby a portion of exhaust gases may pass from sai/l inlet tube intosaid spiral arresting member and another portion may pass around theclosed end of 6 the inlet tube into the discharge tube therebypreventing generation of excessive back pressure in the device.

2. A compact spark arrester as indicated in claim 15 wherein the spiralarresting member extends from end wall to end Wall in said casing andincludes a free longitudinal edge in spaced relation to said cylindricalcasing.

3. A spark arrester as stated in claim 15 wherein the arresting memberincludes an inner longitudinal marginal edge and an outer longitudinalmarginal edge, a portion of the inner marginal edge being secured to theflared edge portion of said tube and the outer marginal edge is inspaced relation to said cylindrical casing and extends in a zone withina narrow radial angle with respect to said inner edge.

References Cited UNITED STATES PATENTS 472,310 4/ 1892 Mosher 55-452677,357 7/ 1901 Hyde 55-455 869,680 10/1907 Aitken et al 55-461 943,23312/1909 Boyle 181--66 2,600,262 6/ 1952 Powers 55-276 FOREIGN PATENTS164,348 7/ 1955 Australia.

100,275 1/ 1962 Netherlands.

675,399 7/ 1952 Great Britain.

FRANK W. LUTTER, Primary Examiner. B. NOZICK, Assstant Examiner.

